1. Field of the Invention
The present invention relates to honeycomb core panels which are made of a thin metal material, e.g., titanium. Such panels are comprised of a honeycomb core sandwiched between a pair of face sheets. Typically, the core is formed of a plurality of corrugated ribbons or strips which are secured together by welding or otherwise to form a honeycomb structure. The face sheets are welded or diffusion bonded to the edges of the core ribbons. Such structures are characterized by very light weight and extreme rigidity. This type of panel is typically employed in aircraft and naval vessels.
2. Description of the Prior Art
In order to facilitate the welding of the face sheets to the honeycomb core, the core strips used to form the core are provided with flanges at their edges. These flanges are integral with the core strips and are formed during the punching of flat metal strips into the corrugated core strips. The flanges are formed by bending the edges of the core strip so as to be perpendicular to the corrugations. The core strip includes troughs and peaks, and the bending operation causes the flange material to be gathered at the trough areas.
In forming the honeycomb core, the core strips are positioned in an internesting relationship, with the flanges of one core strip ovelapping the flanges of an adjacent core strip. Typically, the portion of the flanges at the troughs in each strip are "joggled", i.e., bent inward slightly, to facilitate the internesting of the core strips. The portion of the flange adjacent the peaks of one core strip are slid over the portion of the flange at the troughs of another core strip, with the resulting structure presenting a substantially flat surface at the flanges for securing to the face sheets.
In prior art designs, the gathered portion of the flange at the trough is folded back upon itself during the bending operation which forms the flanges. The flanges thus have a triple thickness at the troughs. Although such a structure is adequate for many applications, its use is typically restricted to core materials having a thickness of about 5 mils or less. Because of the triple thickness of the flange at the trough, the buildup of material limits the thickness of material which can be used to form the core.